The present invention relates to a method of manufacturing caliper bodies of vehicular disc brakes and to a caliper body.
A vehicular disc brake is so arranged as to obtain braking force by pressing a pair of frictional pads disposed opposite to each other with a disc rotor held therebetween to contact respective disc surfaces.
A typical vehicular disc brake is arranged so that braking force is obtained by pressing a pair of frictional pads disposed opposite to each other with a disc rotor held therebetween to contact respective disc surfaces. The caliper body of the disc brake is designed to support the frictional pads in such a way as to be press-contact the disc rotor contains a piston for pressing the disc rotor under pressure.
Generally, iron is used to make a caliper body of the sort mentioned above by casting. However, in recent years, there has developed a demand for making caliper bodies of disc brakes more lightweight and this has resulted in studying the possibilities of manufacturing caliper bodies by using lighter aluminum or aluminum alloy in place of iron. The use of aluminum or aluminum alloy for manufacturing caliper bodies can contribute to reducing their weight in comparison with the iron products.
In view of reliability, caliper bodies of disc brakes need to have sufficient rigidity. Nevertheless, in a case where aluminum or aluminum alloy is employed for making such a caliper body by casting, the strength of the product poses a problem in view of reliability. When the gravity casting method (GDC) as a relatively easy casting method is relied upon, it would be necessary to sufficiently direct attention to sink marks and the like of casts to secure sufficient rigidity. In the case of employing aluminum and aluminum alloy, temperature control is severe and unless the casting method is set in consideration of molten metal running efficiency, nonconformity such as sink marks of casts will come to be produced with a decrease in a yield rate as well as productivity. When the caliper body is made by casting, particularly by the gravity casting method, the selection of the site of providing a sprue becomes an important condition to ensure that a mold is filled up with molten metal to eliminate a sink mark in the cast.